System and Method for Digital Cancellation of Self-Interference in Full-Duplex Communications

• US 20160056946A1
• Filed: 08/20/2014
• Published: 02/25/2016
• Est. Priority Date: 08/20/2014
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Moher, Michael
• Granted Patent: US 9,847,865 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex

Abstract

Embodiments are provided for cancelling self-interference in a full-duplex communications system. The cancellation includes using a digital cancellation stage in additional to analog cancellation. In an embodiment, a method by a full-duplex communications device includes sampling a received signal, wherein the sampling provides a received digital signal corresponding to the received signal. The method further includes sampling a transmitted signal, wherein the sampling provides a transmitted digital signal corresponding to the transmitted signal. A channel distortion introducing self-interference in the received signal is then estimated according to the transmitted digital signal and the received digital signal. The method further includes estimating the self-interference in the received digital signal according to the estimated channel distortion.

Claims

1. A method for execution by a full-duplex communications device, the method comprising:

sampling a received signal to obtain a received digital signal corresponding to the received signal;

sampling a transmitted signal to obtain a transmitted digital signal corresponding to the transmitted signal;

estimating a channel distortion introducing self-interference in the received signal in accordance with the transmitted digital signal and the received digital signal; and

estimating the self-interference in the received digital signal according to the estimated channel distortion.

2. The method of claim 1 further comprising, before estimating the channel distortion, buffering the received digital signal according to a defined number of sampling points for the received signal.

3. The method of claim 1 further comprising obtaining an improved received signal by removing the estimated self-interference from the received digital signal.

4. The method of claim 1 further comprising rejecting the transmitted signal from a reception path for the received signal at an isolation circuit positioned at an intersection of a transmission path for the transmitted signal and the reception path.

5. The method of claim 1 further comprising:

before the sampling, estimating a second channel distortion in the received signal according to the transmitted signal and the received signal;

estimating a second self-interference in the received signal according to the estimated second channel distortion in the received signal; and

removing the estimated second self-interference in the received signal before removing the estimated self-interference from the received digital signal, wherein the estimated self-interference is residual self-interference after removing the estimated second self-interference.

6. A method by a full-duplex communications device, the method comprising:

sampling a transmitted signal from the full-duplex communications device;

sampling a received signal at the full-duplex communications device;

estimating channel characteristics for self-interference according to the sampled transmitted signal, the sampled received signal, and a model relating the received signal to the transmitted signal and the channel characteristics; and

estimating the self-interference in the received signal according to the estimated channel characteristics.

7. The method of claim 6 further comprising removing the estimated self-interference from the received signal.

8. The method of claim 6, wherein the model is a linear model relating a row vector of the sampled received signal to a product of a data matrix according to the sampled transmitted signal and a column vector of the channel characteristics, and wherein estimating the channel characteristics comprises solving for the column vector in the linear model using a suitable algorithm.

9. The method of claim 8, wherein the suitable algorithm is a minimum square error (MSE) solution.

10. The method of claim 8, wherein the row vector of the sampled received signal has a first length equal to a number of sampled signals, and wherein the column vector of the channel characteristics has a second length equal to a dimension suitable for the channel characteristics.

11. The method of claim 10, wherein the number of sampled signals exceeds the dimension for the channel characteristics.

12. A communications device for full-duplex communications, the communications device comprising:

a transmitter chain configured to transmit a first signal;

a receiver configured to receive a second signal;

an antenna coupled to the transmitter chain and the receiver;

a passive analog cancellation circuit positioned between the transmitter chain, receiver, and the antenna, and configured to reject the first signal from a reception path between the passive analog cancellation circuit and the receiver; and

a digital cancellation circuit coupled to the receiver and the transmitter chain, and configured to sample the first signal and the second signal, and estimate self-interference in the sampled second signal according to the sampled first signal and an estimate of a distortion channel inside the communications device.

13. The communications device of claim 12, wherein the digital cancellation circuit is further configured to remove the estimated self-interference from the sampled second signal.

14. The communications device of claim 12, wherein the distortion channel represents self-interference in the second signal due to multiple reflections of the first signal and the second signal along multiple paths in the communications device.

15. The communications device of claim 12, wherein the digital cancellation circuit is further configured to buffer a defined number of samples of the second signal before estimating the self-interference.

16. The communications device of claim 12 further comprising an active analog cancellation circuit positioned between the passive analog cancellation circuit, the transmitter chain, and the receiver, and configured to estimate a second self-interference in the second signal according to the first signal and an estimate of a second distortion channel inside the communications device.

17. The communications device of claim 16, wherein the active analog cancellation circuit is further configured to remove the second self-interference from the second signal before removing the self-interference from the sampled second signal, wherein the estimated self-interference corresponds to residual self-interference after removing the estimated second self-interference.

18. The communications device of claim 16, wherein the active analog cancellation circuit includes:

a secondary receiver coupled to the passive analog cancellation circuit;

a secondary transmitter coupled to the receiver; and

a channel estimation circuit coupled to the secondary receiver, the secondary transmitter, and the transmitter chain.

19. The communications device of claim 12, wherein the transmitter chain includes a baseband transmitter and a radio frequency (RF) signal transmitter in series.

20. The communications device of claim 12 further comprising an analog to digital converter (ADC) positioned between the receiver and the digital cancellation circuit.